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  <script>
    // 题目1(选做)：const arr=['name','age','hhh','hhh','age','hhh','hhh','hhh']各出现多少次
    // 要求输出一个对象如下：{age: 2,hhh: 5,name: 1}
    const arr = ['name', 'age', 'hhh', 'hhh', 'age', 'hhh', 'hhh', 'hhh']
    const obj = {}
    for (let i = 0; i < arr.length; i++) {
      if (!obj[arr[i]]) {
        obj[arr[i]] = 1
      } else {
        obj[arr[i]]++
      }
    }
    console.log(obj);
    // 题目2(必做)：现在两个数组，判断在a中的元素，不在b中 const a = [1,2,3,5] const b=[1,3,5,6] 将在a不在b中的筛选出来
    // 要求：输出一个数组：[2]
    const a = [1, 2, 3, 5]
    const b = [1, 3, 5, 6]
    const c = []
    for (let i = 0; i < a.length; i++) {
      if (b.indexOf(a[i]) === -1) {
        c.push(a[i])
      }
    }
    for (let i = 0; i < a.length; i++) {
      if (!b.includes(a[i])) {
        c.push(a[i])
      }
    }
    console.log(c);
    // 题目3(必做):数组去重(可以用多种方法,至少写一种)
    // 要求：输出一个数组：[1,2,3,9]
    const arr2 = [1, 2, 3, 2, 9]
    const arr3 = []
    for (let i = 0; i < arr2.length; i++) {
      if (arr3.indexOf(arr2[i]) === -1) {
        arr3.push(arr2[i])
      }
    }
    for (let i = 0; i < arr2.length; i++) {
      if (!arr3.includes(arr2[i])) {
        arr3.push(arr2[i])
      }
    }
    console.log(arr3);
  </script>
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